Enhanced Thermoelectric Transport Properties in Cu-added Bi2Se3 Polycrystalline Alloys

Abstract

The addition of Cu to layered Bi2Te3-based thermoelectric alloys has been studied as an effective way to enhance thermoelectric transport properties. In this study, the influence of adding Cu to Bi2Se3 alloys, which have the same rhombohedral crystal structure as Bi2Te3, was investigated by synthesizing a series of CuxBi2Se3 (<i>x</i> = 0, 0.004, 0.008, 0.012, and 0.016) alloys. The power factors of all the Cu-added samples were enhanced compared with that of the pristine Bi2Se3 sample, primarily because of the increase in electrical conductivity. The power factor for the Cu0.016Bi2Se3 sample (<i>x</i> = 0.016) was 0.80 mW/mK<sup>2</sup>, a 35% increase compared to 0.59 mW/mK<sup>2</sup> for the pristine sample at 520 K. A decrease in the total and lattice thermal conductivity was observed for the Cu-added samples, caused by additional point defect scattering after doping. The lattice thermal conductivity of the Cu0.016Bi2Se3 sample (<i>x</i> = 0.016) was 0.56 W/mK, a 42% reduction. Consequently, the zT values of all the Cu-added samples were enhanced, and the maximum zT value was 0.38 for the Cu0.016Bi2Se3 sample (<i>x</i> = 0.016) at 520 K, a 48% increase compared to that of pristine Bi2Se3. The phenomenological transport parameters, including density of state, effective mass, weighted mobility, and thermoelectric quality factor, were calculated to analyze the enhanced electronic transport properties of the Cu-added Bi2Se3.